Idaho, as in the rest of the Pacific Northwest, is turning into a region where almost all of the growth and job opportunities are concentrated in the population centers, a state report says.

Population increases, more jobs and construction spending all indicate general stagnation in rural areas of the state but thriving growth in the population centers of Ada, Canyon, Bonneville and Kootenai counties.That's the report from the Division of Financial Management in its monthly newsletter, "Idaho Outlook," published Thursday.

As evidence that "Two Idahos" are developing, the agency said between 1980 and 1985, Idaho's population grew by 60,000 and 60 percent of the growth occurred in Ada, Canyon, Bonneville and Kootenai counties.

Population in those four counties went up 9.4 percent. The rest of the state grew by 4.2 percent.

Between 1982 and 1987, total employment in Idaho went up 13,100, but in the four counties, it increased 21,600. Employment dropped in more than half of Idaho's counties during the period, DFM said.

Ada and Bonneville counties have consistently averaged nearly 2 percentage points below the statewide unemployment rate, the report said. But both Canyon and Kootenai have had higher than average unemployment.

Construction reports also indicate growth is occurring in small pockets of the state.

According to the Idaho Construction Report, 80.5 percent of the construction value generated so far this year has occurred in Ada, Bonneville and Kootenai counties. Over the last three years, 60 percent of Idaho construction has been in those counties and their cities of Boise, Idaho Falls and Coeur d'Alene.

The report said Boise, in particular, is enjoying a long-awaited construction boom. Nonresidential projects now under way or firmly scheduled for this year will be worth at least $90 million. Nearly half will be public works projects, including construction of a new prison, the Broadway-Chinden Connector, expansion of the Idaho Veterans' Home, the downtown transit mall and major street reconstruction.

Several major commercial developments have been started or have been announced, the report said, which easily could double the $90 million in construction activity.

"To put this long-awaited building boom in perspective, Boise averaged $18 million in nonresidential construction in 1984-84, before jumping to $57.3 million in 1987 as some of these projects began.

"While this activity will provide a boost to the state's economy in the short run, and will help cement Boise's role as a regional economic center, it does contribute to the issue of `Two Idahos,' " the report said.

But the Division of Financial Management said the outlook is not all bleak for outlying areas. Resource industries are notoriously cyclical, and agriculture, forestry and mining all have experienced hard times during the 1980s.

"Prospects have now improved somewhat for all three, but the economies of rural communities remain very fragile," the report said.

"Perhaps the message is that many economic development efforts naturally tend to favor a handful of larger cities, especially in the area of attracting new business.